1. Technical Field
The present invention relates to a transformer and a complementary metal-oxide-semiconductor (CMOS) power amplifier including the same, and more particularly, to a transformer in which structures of primary and secondary coils may be improved to improve power transmission efficiency, and a CMOS power amplifier including the same.
2. Description of the Related Art
In general, in a wireless communication system such as a mobile communication terminal, a power amplifier is used to transmit and receive signals in a wireless manner.
The power amplifier refers to a device that efficiently amplifies minute signals to larger signals with small distortion and supplies the amplified signals to a load via an antenna. The power amplifier is classified, according to frequencies, as a low-frequency power amplifier and a high-frequency power amplifier.
In addition, the power amplifier also includes a complementary metal-oxide-semiconductor (CMOS) power amplifier which is designed using a general-purpose CMOS process with a process of GaAs, which is a special semiconductor Since the CMOS power amplifier may be mass-produced, the costs therefor may be reduced, and various functions may be included in the CMOS power amplifier.
The CMOS power amplifier includes a driver amplifying unit and a power amplifying unit, and the driver amplifying unit and the power amplifying unit are provided in a differential structure in which they amplify signals of different phases. In addition, a transformer is included between the driver amplifying unit and the power amplifying unit for matching.
However, according to the conventional art, when forming the transformer, a primary coil and a secondary coil are implemented on the same plane, and when the primary coil and the secondary coil are implemented on the same plane, a coupling efficiency decreases, as the coupling efficiency is decreased, the power transmission efficiency also decreases.
In addition, when the primary coil and the secondary coil are disposed too close to each other on the same plane, problems such as a short circuit may be generated.
Thus, a method of increasing the power transmission efficiency by improving the structures of the primary and secondary coils of the transformer to dispose the primary and secondary coils close to each other while preventing a short circuit is suggested.